Photographing condition determining method for metal structure, photographing method for metal structure, phase classification method for metal structure, photographing condition determining device for metal structure, photographing device for metal structure, phase classification device for metal structure, material property estimating method for metal material, and material property estimating device for metal material

Abstract

A photographing condition determining method includes: photographing a part of a metal structure of a metal material subjected to predetermined sample preparation under a predetermined photographing condition; assigning, to pixels corresponding to one or a plurality of predetermined phases of the metal structure, labels of respective phases for a photographed image; calculating one or more feature values for a pixel to which a label of one of the assigned phases; classifying the phases of the metal structure of the image by inputting a calculated feature value to a model, which has been learned in advance using feature values assigned with labels of respective phases as input and labels of the respective phases as output, and acquiring a label of a phase of a pixel corresponding to the input feature value; and determining a photographing condition when other parts of the metal structure are photographed based on a classification result.

The invention claimed is: 
     
       1. A photographing condition determining method for photographing a metal structure of a metal material, the photographing condition determining method comprising:
 a photographing step of photographing a part of the metal structure of the metal material having been subjected to predetermined sample preparation under a predetermined photographing condition; 
 a phase specification step of assigning, to pixels corresponding to one or a plurality of predetermined phases of the metal structure, labels of respective phases for an image photographed in the photographing step; 
 a feature value calculating step of calculating one or more feature values for a pixel to which a label of one of the phases has been assigned in the phase specification step; 
 a phase classification step of classifying the phases of the metal structure of the image by inputting a feature value calculated in the feature value calculating step to a model, which has been learned in advance using feature values assigned with labels of respective phases as input and labels of the respective phases as output, and acquiring a label of a phase of a pixel corresponding to the feature value that has been input; and 
 a photographing condition determining step of determining a photographing condition when other parts of the metal structure are photographed based on a classification result of the phase classification step. 
 
     
     
       2. The method according to  claim 1 ,
 wherein, in the photographing step, a part of the metal structure is photographed under a plurality of predetermined photographing conditions, and 
 in the photographing condition determining step, a photographing condition with which a classification accuracy of the phases in the phase classification step is the highest among the plurality of photographing conditions used in the photographing step is determined as a photographing condition for photographing the other parts of the metal structure. 
 
     
     
       3. The method according to  claim 1 , wherein the photographing condition includes at least one of a contrast value, a brightness value, and an intensity of a light source. 
     
     
       4. The method according to  claim 1 , further comprising, before the photographing step:
 a polishing step of roughly polishing the metal material and then performing buffing using a polishing material of 0.05 μm to 2 μm; and 
 an etching step of etching the metal material using a nital solution prepared by mixing ethanol and nitric acid and has a nitric acid concentration of 0.5% to 8%. 
 
     
     
       5. A photographing method for a metal structure, wherein the other parts of the metal structure of the metal material are photographed under the photographing condition determined by the photographing condition determining method after the photographing condition determining method for a metal structure according to  claim 1 . 
     
     
       6. A phase classification method for a metal structure, comprising the steps of: photographing the metal structure by the photographing method for a metal structure according to  claim 5 ; and classifying phases of the metal structure. 
     
     
       7. A material property estimating method for a metal material for estimating a material property of the metal material, the material property estimating method comprising, after the method according to  claim 6 :
 a quantitative evaluation step of calculating a quantitative evaluation value of the metal structure by calculating a size, an area ratio, or a shape of each of the classified phases; 
 a data selection step of selecting data to be used for estimation of a material property of the metal material from the quantitative evaluation value and material properties of the metal material prepared in advance; 
 a model generating step of generating an estimation model for estimating a material property of the metal material using the data that has been selected; and 
 a material property estimating step of estimating a material property of the metal material using the estimation model that has been generated. 
 
     
     
       8. A photographing condition determining method for photographing a metal structure of a metal material, the photographing condition determining method comprising:
 a photographing step of consecutively photographing a part of the metal structure having been subjected to predetermined sample preparation while a photographing condition is varied; 
 a feature value calculating step of calculating one or more feature values for images photographed in the photographing step; 
 a phase classification step of classifying phases of the metal structure of the image by inputting a feature value calculated in the feature value calculating step to a model, which has been learned in advance using feature values of pixels assigned with labels of one or a plurality of predetermined phases of the metal structure as input and labels of the respective phases as output, and acquiring a label of a phase of a pixel corresponding to the feature value that has been input; and 
 a photographing condition determining step of determining a photographing condition when other parts of the metal structure are photographed from among a plurality of photographing conditions used in the photographing step based on a classification result of the phase classification step. 
 
     
     
       9. The method according to  claim 8 , wherein, in the photographing condition determining step, a photographing condition under which a classification accuracy of the phases in the phase classification step is a highest among the photographing conditions used in the photographing step is determined as a photographing condition for photographing the other parts of the metal structure. 
     
     
       10. The method according to  claim 8 , wherein the photographing condition includes at least one of a contrast value, a brightness value, and an intensity of a light source. 
     
     
       11. The method according to  claim 8 , further comprising, before the photographing step:
 a polishing step of roughly polishing the metal material and then performing buffing using a polishing material of 0.05 μm to 2 μm; and 
 an etching step of etching the metal material using a nital solution which is prepared by mixing ethanol and nitric acid and has a nitric acid concentration of 0.5% to 8%. 
 
     
     
       12. A photographing method for a metal structure, wherein the other parts of the metal structure of the metal material are photographed under the photographing condition determined by the photographing condition determining method after the method according to  claim 8 . 
     
     
       13. A phase classification method for a metal structure, comprising the steps of: photographing the metal structure by the method according to  claim 12 ; and classifying phases of the metal structure. 
     
     
       14. A photographing condition determining device for photographing a metal structure of a metal material, the photographing condition determining device comprising:
 a photographing unit that photographs a part of the metal structure of the metal material having been subjected to predetermined sample preparation under a predetermined photographing condition; 
 a phase specification unit that assigns, to pixels corresponding to one or a plurality of predetermined phases of the metal structure, labels of respective phases for an image photographed by the photographing unit; 
 a feature value calculating unit that calculates one or more feature values for a pixel to which a label of one of the phases has been assigned by the phase specification unit; 
 a phase classification unit that classifies the phases of the metal structure of the image by inputting a feature value calculated by the feature value calculating unit to a model, which has been learned in advance using feature values assigned with labels of respective phases as input and labels of the respective phases as output, and acquiring a label of a phase of a pixel corresponding to the feature value that has been input; and 
 a photographing condition determining unit that determines a photographing condition when other parts of the metal structure are photographed based on a classification result of the phase classification unit. 
 
     
     
       15. A photographing device for a metal structure, wherein the other parts of the metal structure of the metal material are photographed under the photographing condition determined by the photographing condition determining device according to  claim 14 . 
     
     
       16. A phase classification device for a metal structure, wherein the metal structure is photographed by the photographing device for a metal structure according to  claim 15 , and phases of the metal structure are classified. 
     
     
       17. A photographing condition determining device for photographing a metal structure of a metal material, the photographing condition determining device comprising:
 a photographing unit that consecutively photographs a part of the metal structure having been subjected to predetermined sample preparation while a photographing condition is varied; 
 a feature value calculating unit that calculates one or more feature values for images photographed by the photographing unit; 
 a phase classification unit that classifies phases of the metal structure of the image by inputting a feature value calculated in the feature value calculating unit to a model, which has been learned in advance using feature values of pixels assigned with labels of one or a plurality of predetermined phases of the metal structure as input and labels of the respective phases as output, and acquiring a label of a phase of a pixel corresponding to the feature value that has been input; and 
 a photographing condition determining unit that determines a photographing condition when the other parts of the metal structure are photographed from among a plurality of photographing conditions used in the photographing unit based on a classification result of the phase classification unit. 
 
     
     
       18. A photographing device for a metal structure, wherein the other parts of the metal structure of the metal material are photographed under the photographing condition determined by the device according to  claim 17 . 
     
     
       19. A phase classification device for a metal structure, wherein the metal structure is photographed by the device according to  claim 18 , and phases of the metal structure are classified. 
     
     
       20. A material property estimating device for a metal material for estimating a material property of the metal material, the material property estimating device comprising:
 an input unit that inputs an image in which phases of a metal structure have been classified; 
 a quantitative evaluation unit that calculates a quantitative evaluation value of the metal structure by calculating a size, an area ratio, or a shape of each of the classified phases; 
 a data recording unit that records the quantitative evaluation value in a database; 
 a data selection unit that selects data to be used for estimation of a material property of the metal material from among the quantitative evaluation value and material properties of the metal material recorded in the database; 
 a model generation unit that generates an estimation model for estimating a material property of the metal material using the data that has been selected; 
 a material property estimating unit that estimates a material property of the metal material using the estimation model that has been generated; and 
 an output unit that outputs the material property of the metal material that has been estimated.